AN Fittings 101:
At Full Send Diesel, we got tired of dealing with weak fittings, sloppy threads, and backorders—so we made our own. Our full line of AN fittings, adapters, hose ends, and braided hose is fully stocked right here in New Jersey and ships fast.
Whether you’re plumbing a full fuel system, setting up a catch can, or running custom coolant lines, we’ve got you covered. We’re one of the largest sellers of AN fittings and pre-made hose kits in the country—because we actually use this stuff ourselves on real builds.
What Are AN Fittings?
AN stands for “Army-Navy,” but in the performance world, it just means clean, reliable, high-pressure fittings. AN fittings use a 37° flare to seal, making them perfect for fuel, oil, coolant, or transmission fluid. They’re modular, leak-proof, and way easier to work with than hose clamps and push-locks.
Common AN Sizes:
- -3AN = 3/16"
- -4AN = 1/4"
- -6AN = 3/8"
- -8AN = 1/2"
- -10AN = 5/8"
- -12AN = 3/4"
- -16AN = 1"
- -20AN = 1-1/4"
Understanding Adapter Types
Not all threads are AN. Here's what you need to know before grabbing the wrong fitting:
NPT (National Pipe Thread)
Tapered threads that seal as they tighten. Common on older fuel pumps, sensors, and manifolds. Requires thread sealant or PTFE tape.
ORB (O-Ring Boss)
Straight threads that seal with an O-ring at the base. Common on billet valve covers, fuel rails, and regulators. No tape needed—clean and reusable.
Metric Adapters
Used when tapping into OEM ports like fuel rails or turbo feeds. Threads vary (M12x1.5, M14x1.5, etc). Use our metric to AN adapters to convert to AN fittings.
How to Assemble AN Hose (Step-by-Step)
- Cut the hose clean: Use a cutoff wheel or hose shears. Wrap in tape before cutting to keep the braid tight.
- Insert into the socket: Push the hose into the socket until it bottoms out. It may take some force—a vise helps.
- Lubricate threads: Use oil or anti-seize to prevent galling.
- Thread it together: Tighten the fitting into the socket using two wrenches. Stop when there’s about a 1/32" gap left.
- Check your work: Visually inspect and pressure test if possible before final install.
AN Size Reference Chart
| AN Size | Hose I.D. | Thread Size (UNF) | Wrench Size |
|---|---|---|---|
| -3AN | 3/16" | 3/8-24 | 3/8" |
| -4AN | 1/4" | 7/16-20 | 7/16" |
| -6AN | 3/8" | 9/16-18 | 11/16" |
| -8AN | 1/2" | 3/4-16 | 7/8" |
| -10AN | 5/8" | 7/8-14 | 1" |
| -12AN | 3/4" | 1-1/16-12 | 1-1/4" |
| -16AN | 1" | 1-5/16-12 | 1-1/2" |
| -20AN | 1-1/4" | 1-5/8-12 | 1-7/8" |
Why Our Fittings?
- 6061 CNC-machined aluminum
- Black anodized for corrosion resistance
- Built by diesel guys, for diesel guys
- In stock & shipping same-day from NJ
Common Uses for AN Plumbing
- Fuel systems (feed & return)
- Lift pump to engine connections
- Regulated return kits
- Catch can setups
- Transmission cooler lines
- Turbo oil feed & drain
- Custom coolant reroutes
Need Help Choosing the Right Fittings?
If you’re building a custom setup and not sure what you need, reach out. We’ll help you piece together the exact parts for your layout—no guesswork, no frustration.
Everything is in stock now. No dropshipping. No delays. Just fast shipping and parts that work.